Impact of extreme weather on coral reefs

Coral reefs can cope with natural disturbances like floods and cyclones, however extreme intensity weather is rare and often causes severe and widespread damage that takes decades to recover.

The extreme weather that affected the Great Barrier Reef in the summer of 2010-11 potentially caused levels of damage that have been experienced only rarely over recent decades or centuries.

Floods and cyclone affect the Great Barrier Reef ecosystem in different ways.

Floods

Floodwaters running off the land and into the Great Barrier Reef lagoon can form reduced-salinity plumes laden with nutrients, sediments and agricultural chemicals such as fertilizers and pesticides.

Many animals and plants that inhabit coral reef ecosystems can be stressed or killed through reduced salinity, increased turbidity and elevated concentrations of nutrients and agricultural chemicals.

Some species can benefit from the increased input of materials like nutrients, leading to excessive productivity in certain groups, such as algae, which can create imbalances in the system.

Cyclones

Tropical cyclones are major structuring forces on coral reefs, causing extensive damage to individual corals and to the structure of the Reef.

Between 1995 and 2009, approximately 34 per cent of all coral mortality recorded in the Great Barrier Reef Long Term Monitoring Program (implemented by the Australian Institute of Marine Science) has been caused by storm damage.

Among cyclones, extreme intensity systems such as cyclone Yasi are particularly important influences on coral reefs, as they can have impacts that affect large areas and last for decades, if not centuries.